{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,30]],"date-time":"2026-04-30T11:37:23Z","timestamp":1777549043981,"version":"3.51.4"},"reference-count":51,"publisher":"MDPI AG","issue":"7","license":[{"start":{"date-parts":[[2025,7,11]],"date-time":"2025-07-11T00:00:00Z","timestamp":1752192000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Hugel Inc.","award":["IIT-HG-Tx-20250610-01"],"award-info":[{"award-number":["IIT-HG-Tx-20250610-01"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Toxins"],"abstract":"<jats:p>Background: Melasma is an acquired hyperpigmentation disorder with multifactorial etiologies and limited response to conventional therapies. Recent evidence suggests that Botulinum Toxin A (BoNT-A) may modulate ultraviolet (UV)-induced pigmentation and offer therapeutic benefits. Objective: We sought to evaluate the efficacy and safety of two intradermal dilutions of Letibotulinum toxin A (LetiBoNT-A) in Thai patients with melasma. Methods: In this randomized, double-blind, split-face study, 30 participants aged 32\u201362 years received a single intradermal injection of LetiBoNT-A, with 20 units administered per cheek. A 1:5 dilution was injected on one side of the face, and a 1:10 dilution was injected on the contralateral side. Outcomes were evaluated over a 6-month period using the Hemi-modified Melasma Area and Severity Index (Hemi-mMASI), VISIA\u00ae brown spot analysis, and quantitative assessments of skin texture. Results: Both dilutions significantly improved Hemi-mMASI scores (1:5, p = 0.043; 1:10, p = 0.002) and brown spots (1:5, p = 0.002; 1:10, p &lt; 0.001). The 1:10 dilution showed earlier and more sustained improvements. Subgroup analysis revealed greater reductions in Hemi-mMASI scores among patients with telangiectatic melasma, particularly with the 1:10 dilution, though they were not statistically significant. Additionally, the 1:10 dilution significantly reduced pore volume, pore area, and sebum levels. One case of transient facial asymmetry was reported with the 1:5 dilution. Conclusions: LetiBoNT-A is a safe and effective adjunct in melasma treatment. The 1:10 dilution offered superior clinical outcomes.<\/jats:p>","DOI":"10.3390\/toxins17070349","type":"journal-article","created":{"date-parts":[[2025,7,11]],"date-time":"2025-07-11T12:46:33Z","timestamp":1752237993000},"page":"349","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":2,"title":["Efficacy and Safety of Letibotulinum Toxin A for the Treatment of Melasma in Two Different Dilutions: A Randomized Double-Blind Split-Face Study"],"prefix":"10.3390","volume":"17","author":[{"ORCID":"https:\/\/orcid.org\/0009-0001-1018-6780","authenticated-orcid":false,"given":"Juthapa","family":"Pongklaokam","sequence":"first","affiliation":[{"name":"Department of Dermatology, Faculty of Medicine Siriraj Hospital, Mahidol University, 2 Wanglang Road, Bangkok Noi, Bangkok 10700, Thailand"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-8393-7963","authenticated-orcid":false,"given":"Woraphong","family":"Manuskiatti","sequence":"additional","affiliation":[{"name":"Department of Dermatology, Faculty of Medicine Siriraj Hospital, Mahidol University, 2 Wanglang Road, Bangkok Noi, Bangkok 10700, Thailand"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-3926-2193","authenticated-orcid":false,"given":"Rungsima","family":"Wanitphakdeedecha","sequence":"additional","affiliation":[{"name":"Department of Dermatology, Faculty of Medicine Siriraj Hospital, Mahidol University, 2 Wanglang Road, Bangkok Noi, Bangkok 10700, Thailand"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Pitchaya","family":"Maneeprasopchoke","sequence":"additional","affiliation":[{"name":"Department of Dermatology, Faculty of Medicine Siriraj Hospital, Mahidol University, 2 Wanglang Road, Bangkok Noi, Bangkok 10700, Thailand"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Panwadee","family":"Thongjaroensirikul","sequence":"additional","affiliation":[{"name":"Department of Dermatology, Faculty of Medicine Siriraj Hospital, Mahidol University, 2 Wanglang Road, Bangkok Noi, Bangkok 10700, Thailand"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Yanin","family":"Nokdhes","sequence":"additional","affiliation":[{"name":"Department of Dermatology, Faculty of Medicine Siriraj Hospital, Mahidol University, 2 Wanglang Road, Bangkok Noi, Bangkok 10700, Thailand"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Rona Maria R.","family":"Abad-Constantino","sequence":"additional","affiliation":[{"name":"Department of Dermatology, Research Institute for Tropical Medicine, 9002 Research, Mutinlupa 1781, Philippines"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0009-0002-1092-455X","authenticated-orcid":false,"given":"Woramate","family":"Bhorntarakcharoen","sequence":"additional","affiliation":[{"name":"Department of Dermatology, Faculty of Medicine Siriraj Hospital, Mahidol University, 2 Wanglang Road, Bangkok Noi, Bangkok 10700, Thailand"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Sariya","family":"Sittiwanaruk","sequence":"additional","affiliation":[{"name":"Department of Dermatology, Faculty of Medicine Siriraj Hospital, Mahidol University, 2 Wanglang Road, Bangkok Noi, Bangkok 10700, Thailand"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9590-8887","authenticated-orcid":false,"given":"Thanya","family":"Techapichetvanich","sequence":"additional","affiliation":[{"name":"Department of Dermatology, Faculty of Medicine Siriraj Hospital, Mahidol University, 2 Wanglang Road, Bangkok Noi, Bangkok 10700, Thailand"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2025,7,11]]},"reference":[{"key":"ref_1","first-page":"939","article-title":"Disorders of hyperpigmentation","volume":"2","author":"Chang","year":"2008","journal-title":"Dermatology"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"3432","DOI":"10.1111\/jocd.14382","article-title":"The pathogenesis of melasma and implications for treatment","volume":"20","author":"Artzi","year":"2021","journal-title":"J. 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